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To better control drug delivery rate, a simple and effective approach has been developed for controlled drug delivery carrier system through one-step surface modification of the ibuprofen-impregnated silica MCM-41 with 1, 1, 1, 3, 3, 3-hexamethyldisilazane (HMDS). The 29Si MAS NMR characterization demonstrated that different contents of trimethylsilyl (TMS) groups were successfully grafted onto the samples modified with different silylation times. The results obtained from in vitro tests exhibited that the introduction of TMS groups greatly retarded the ibuprofen release rate. Even after in vitro test for 48 h, only 75% of the impregnated ibuprofen could be released from the modified sample with TMS groups content of 14.5% (related to the total silicon atoms). However, the release of ibuprofen could be completed just after about 1 h from the pure silica MCM-41 under the same release conditions. Furthermore, the release rate of ibuprofen could be well modulated by changing the grafted content of TMS groups, and was found to decrease with increasing grafted amount of TMS groups.

Abstract: Mesoporous silica spheres with controllable particle size were synthesized in mixed ethanol–water solvent. These materials possessed same pore size distribution and pore channel geometry. The amount of ibuprofen (IBU) adsorbed in mesoporous channels increased with the surface area of mesoporous silica spheres. Three kinds of release fluids, simulated intestinal fluid (SIF, pH=7.4), simulated body fluid (SBF, pH=7.4), and simulated gastric fluid (SGF, HCl aqueous solution, pH=1.2) were used to investigate drug release. The effects of particle size and dispersancy of mesoporous spheres on drug release rate were discussed in detail. It was found that larger or agglomerate mesoporous silica spheres could delay the drug release process, which could be attributed to pore-mouth amount and mesopore channel length of mesoporous spheres. Furthermore, to obtain a well controlled drug release system, hydrophobic trimethylsilyl (TMS) groups were functionalized on the surface of mesoporous silica spheres. The release of IBU from TMS-functionalized mesoporous spheres was obviously delayed with the increase of TMS content. [Copyright &y& Elsevier]

Abstract: Dimethylsilyl (DMS) modified mesoporous silicas were successfully prepared via co-condensation and post-grafting modification methods. The post-grafting modification was carried out by the reaction of the as-synthesized MCM-41 material (before CTAB removal) with diethoxydimethylsinale (DEDMS). N2 adsorption–desorption and 29Si MAS NMR characterization demonstrated that different amount of DMS groups were successfully incorporated into the co-condensation modified samples, and the functional DMS groups were placed selectively on the pore openings and external pore surfaces in the post-grafting modified samples. Subsequently, the controlled drug delivery properties from the resulting DMS-modified mesoporous silicas were investigated in detail. The drug adsorption experiments showed that the adsorption capacities were mainly depended on the content of silanol group (CSG) in the corresponding carriers. The in vitro tests exhibited that the incorporation of DMS groups greatly retarded the ibuprofen release rate. Moreover, the ibuprofen release profiles could be well modulated by varying DMS modification levels and site-selective distribution of functional groups in mesoporous carriers. [Copyright &y& Elsevier]